To ascertain the relationship between voiding dysfunction associated with diabetes and bladder and sphincter behavior, the video urodynamic studies of 182 patients were retrospectively analyzed. Patients were classified based on urodynamic diagnosis and the presence or absence of signs of sacral cord involvement. Urodynamic findings were classified as either detrusor hyperreflexia, impaired detrusor contractility, detrusor areflexia, indeterminate and normal. The results indicate that mean bladder capacity was 485 +/- 89.3 ml. with a mean first sensation of filling of 298 +/- 67.4 ml. Of the 182 patients 100 (55%) had detrusor hyperreflexia, 42 (23%) had impaired detrusor contractility, 20 (11%) had indeterminate findings, 19 (10%) had detrusor areflexia and 1 (1%) was normal. Bladder outlet obstruction occurred in 66 patients (36%), all men (57%). The diagnosis was isolated in 24 patients (36%) or in combination with another diagnosis in 42 (74%). However, if one considers the presence of sacral cord signs (42 patients), the most common urodynamic diagnoses were either impaired detrusor contractility in 21 (50%) or detrusor areflexia in 10 (24%). These data suggest that classical diabetic cystopathy is not the most common urodynamic findings in patients with diabetes mellitus and voiding dysfunction, and in fact these patients present with variable pathophysiological findings. These findings demonstrate the importance of urodynamic studies in diagnosing voiding dysfunction in diabetics before initiation of therapy.